Method of setting a self-drilling, chemically anchorable fastening element and a self-drilling chemically anchorable fastening element

ABSTRACT

A method of setting a self-drilling chemically anchorable fastening element ( 11; 51 ) includes mounting of an adaptor ( 31 ) on the second end ( 18; 58 ) of the shaft ( 12; 52 ) of the fastening element ( 11; 51 ), connecting the drilling power tool ( 41 ) with the adaptor ( 31 ), the adaptor having an engagement element ( 32 ) for the tool chuck ( 42 ), drilling a borehole ( 7 ) in the constructional component ( 6 ) with the self-drilling fastening element ( 11; 51 ), rotating the fastening element ( 11; 51 ) in a first rotational direction (R 1 ), forcing out the hardenable mass located in the receiving space of the shaft of the fastening element from the fastening element with an ejection device, and pre-stressing the fastening element ( 11; 51 ) after at least partial hardening of the hardenable mass ( 15; 55 ) by rotating the adaptor ( 31 ) in a second rotational direction (R 2 ) opposite the first rotational direction (R 1 ), with at least a section of the adaptor ( 31 ) being displaced in a direction of the first end ( 17; 57 ) of the shaft ( 12; 52 ) of the fastening element.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of setting a self-drilling, chemically anchorable fastening element with use of a drilling power tool and with the fastening element having a shaft with a receiving space for a hardenable mass provided in the fastening element, a drilling head provided at a first end of the shaft, and a thread-shaped outer profile provided at least partially at a second end, with the method including providing an adaptor mountable on the second end of the shaft and having engagement means for a chuck of the drilling power tool and provided on an outer side of the adaptor, and a thread-shaped inner profile complementary to the thread-shaped outer profile on the shaft. The present invention also relates to an improved fastening element adapted to be used with the inventive setting process.

2. Description of the Prior Art

Self-drilling, chemically anchorable fastening elements of the type discussed above are also called chemical shear anchors or rock anchors. Such fastening elements and drilling power tools for setting such fastening elements, as well as their use in mine and tunnel construction are known for a long time. The fastening elements serve primarily for stabilization of walls in hollow spaces, such as tunnels, galleries and the like. During formation of the hollow spaces, mechanical characteristics and particularly, the load-carrying capability of rock layers diminish. Those rock layers are anchored and secured with the fastening elements to more remote, undamaged rock layers.

German Publication DE 103 36 040 A1 discloses a self-drilling, chemically anchorable fastening element for use in tunnel and mine construction. The disclosed fastening element has a hollow cylindrical shaft that serves, on one hand, as a drilling rod and, on the other hand, forms a receiving space for a hardenable mass provided in the fastening element. At the first end of the shaft, a drilling head is provided. The shaft is provided, over its entire longitudinal extent, with a trapezoidal thread in form of thread-shaped profile that extends from the first end of the shaft up to the second end opposite the first end. At the second end of the shaft, an adaptor is provided. The adaptor has, on its outer side, engagement means for a chuck of a drilling power tool suitable for setting the fastening element. The adaptor is further provided with a thread-shaped profile complementary to the trapezoidal thread on the shaft of the fastening element. In one of the embodiment, the adaptor is provided with a predetermined breaking point and has a stop that prevents displacement of least of a section of the adaptor in the direction of the first end of the shaft during a drilling process.

For setting the fastening element according to DE 103 36 040 A1, the adaptor is screwed on the second end of the shaft and is connected with the to-be-used drilling power tool via the tool chuck. Then, the self-drilling fastening element is rotated, via the adaptor, with a small torque and a high rotational speed, forming a borehole in the constructional component.

After a desired borehole depth has been reached, the hardenable mass, which is contained in the receiving space of the shaft of the fastening element, is forced out of the fastening element with an ejection device. The mass is forced out through openings in the region of the first end of the shaft and/or drilling head into an intermediate space between the shaft outer surface and the borehole wall. After the forced-out mass has at least partially hardened, the drilling tool again rotates the adaptor but with a high torque and a lower rotational speed until the adaptor brakes at a predetermined breaking point. For pre-stressing the fastening element, only the free rotating section of the adaptor is displaced in the direction of the first end of the shaft.

The above-described fastening element and the related setting process are characterized by an easy handling. Therefore, the fastening element according to DE 103 36 040 A1 proved itself in practice.

In separate cases, dependant on the type of a constructional component, the adaptor element can break already during the drilling process. If this happens, the drilling tool must be disconnected from the adaptor, and a new adaptor is arranged at the shaft free end with which the drilling tool need again be connected to complete the drilling process.

If a used drilling tool cannot apply an adequate torque to the adaptor for breaking it at the predetermined breaking point, the already set and chemically anchored fastening element is not any more directly pre-stressed. Further, for setting a fastening element, a drilling tool is needed the motor control of which provides for at least two speeds of the motor.

Accordingly, an object of the present invention is a method for setting a fastening element described above the handling of which and reliability are further improved.

Another object of the invention is an improved fastening element adapted to be set using the inventive setting method.

SUMMARY OF THE INVENTION

These and other objects of the present invention, which will become apparent hereinafter, are achieved by providing a setting method as discussed above and that includes further the following steps:

-   -   mounting of the adaptor on the second end of the shaft of the         fastening element;     -   connecting the drilling power tool with the adaptor;     -   drilling a borehole in the constructional component with the         self-drilling fastening element, rotating the fastening element         in a first rotational direction;     -   forcing out the hardenable mass located in the receiving space         from the fastening element with an ejection device, and     -   pre-stressing the fastening element after at least partial         hardening of the hardenable mass by rotating the adaptor in a         second rotational direction opposite the first rotational         direction, so that at least a section of the adaptor is         displaced in a direction of the first end of the shaft of the         fastening element.

With the present invention, breaking of the adaptor under a predetermined load is not anymore necessary for pre-stressing the fastening element and, therefore, the adaptor cannot be broken before the end of a drilling process. Further, no loose parts of the adaptor, which can be produced during breaking of the material, now penetrate in a gap between the shaft of the fastening element and the borehole wall or to penetrate into the fastening element itself. The penetration of the adaptor parts in the gap between the borehole wall and the shaft of the fastening element and the fastening element itself can adversely affect the anchoring of the fastening element.

The setting process according to the present invention permits to apply a maximal torque to the fastening element during drilling of a borehole, which is advantageous, particularly, when drilling hard materials or hard constructional components, as an increased torque increases the drilling speed. In addition, all conventional drilling tools, in particularly those used in underground mines can be used with the inventive setting process.

The hardenable mass is forced out of the fastening element, e.g., with hydraulic, pneumatic, or mechanical means. Advantageously, the ejection device is integrated in the setting tool itself.

The degree of the pre-stress is easily adaptable to the set-ups of the drilling tool. Therefore, there is no need to make available different types of adaptors with differently formed predetermined braking points.

Advantageously, a stop for the adaptor is provided at the second end of the shaft of the fastening element. The stop prevents an undesirable screwing of the adaptor off the second end of the shaft. The stop can be formed, e.g., by a separate element that is mounted on the second end of shaft after the adaptor has been mounted. Advantageously, stop is formed by a fastening element such as, e.g., a pin insertable radially into the shaft of a driven-in fastening element through the adaptor. This pin can be broken at a predetermined torque. Alternatively, a glue point or a soldering point is provided for temporarily secure the adaptor on the shaft.

Advantageously, for drilling a borehole and for pre-stressing the fastening element, a drilling tool with a constant motor is used because with the inventive setting process there is no need in a drilling tool with a variable motor. However, the inventive setting method can also be used with a drilling tool with a variable motor. The inventive setting process permits to optimize in a simple manner the drilling power and the produced pre-stress by a simple adjustment of the drilling tool motor.

Under a constant motor is understood a motor having essentially only one rotational speed. With a hydraulic motor, a constant motor is a fixed displacement motor. Under a variable motor, is understood a motor a rotational speed of which can be arbitrary adjusted. This is because the variable motor has a variable displacement.

Advantageously, the thread-shaped outer profile at the second end of the shaft extends in a direction corresponding to the pre-stressing or second rotational direction. Thereby, during a drilling process, an inadvertent screwing off of the adaptor is prevented. When the fastening element is rotated in a direction opposite the predetermined rotational direction for drilling a borehole, the adaptor is screwed onto the shaft in a direction toward the second end of the shaft of the fastening element.

A fastening element according to the present invention has a thread-shaped outer profile provided at least partially at a second end of the shaft, and a further thread-shaped outer profile extending from the first end of the shaft in a direction corresponding to a first rotational direction of the fastening element. The thread-shaped outer profile that extends from the second end of the shaft, extends in a direction opposite an extension direction of the further thread-shaped outer profile. Thereby, a simple setting of the fastening element is insured.

Advantageously, a pitch of the thread-shaped outer profile extending from the second end of the shaft is flatter than a pitch of the further thread-shaped outer profile. Thereby, with several revolutions, e.g., of the adaptor or a nut, a high pre-stressing force can be obtained.

In case when the amount of the pre-stressing force is secondary and a particularly rapid setting process is required, according to an alternative embodiment of the inventive fastening element, a pitch of the thread-shaped outer profile extending from the second end of the shaft is steeper than a pitch of the further thread-shaped outer profile. The adaptor or the nut is screwed on the shaft until it abuts the constructional component. In this case, a pre-stressing force is provided with fewer revolutions of the adaptor or the nut.

The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiment, when read with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings show:

FIG. 1 a longitudinal cross-sectional view of a fastening element during execution of a drilling step of a method according to the present invention;

FIG. 2 a longitudinal cross-sectional view of a fastening element during execution of an ejection step of the method according to the present invention;

FIG. 3 a longitudinal cross-sectional view of a fastening element during execution of a pre-stressing step of the method according to the present invention; and

FIG. 4 a side view of a fastening element according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In a setting process according to the present invention three separate steps of which are shown in FIGS. 1 through 3, a self-drilling, chemically anchored, fastening element 11 is used. The fastening element 11 has a hollow cylindrical shaft 12 with an inner tube 13 having a receiving space 14 for a hardenable mass 15 provided in the fastening element 11, a drilling head 16 provided on a first end 17 of the shaft 12, and an outer thread provided, at least in one region, on a second end 18 of the shaft 12 and formed as a thread-shaped outer profile 19. The thread-shaped outer profile 19 at the second end 18 of the shaft 12 has a course direction corresponding to the second pre-stressing rotational direction of the fastening element 11.

For an advantageous retaining of the fastening element 11, the hardenable mass 15 is stored in the inner tube 13 in a foil bag. A mixing element 21 is provided between a front end of the foil bag and the first end 17 of the shaft 12. Between the rear end of the foil bag and the second end 18 of the shaft 12, an ejection piston 22 is located in the inner tube 13.

During a setting process, an adaptor 31, which is provided on the second end 18 of the shaft 12, is used. The adaptor 31 has an outwardly arranged, multi-edge element formed as engagement means 32 for a chuck 42 of a drilling power tool 41 suitable for use with such a fastening element, and an inner thread formed as a thread-shaped inner profile 33 complementary to the thread-shaped outer profile 19 on the shaft 12.

After the adaptor 31 has been mounted on the second end 18 of the shaft 12, a stop 36, here, a separate element, for the adapter 31 is provided.

The drilling power tool 41 has a constant motor 43. With the drilling power tool 41, the fastening element 11 is drilled in a constructional component 6 and subsequently, the fastening element is pre-stressed. The drilling power tool 41 also has an ejection device for ejecting the mass 15 stored in the fastening element 11. In the embodiment shown in the drawings, the ejection device is actuated by a high-pressure water and has a feeding nose 46 that in a connected condition of the fastening element with the drilling power tool, sealingly penetrates in the inner tube 13 of the fastening element 11.

The inventive setting method includes the following steps:

Firstly, the adaptor 31 is mounted at the second end 18 of the shaft 12 of the fastening element 11, by being screwed thereon.

Then, the drilling power tool 41 is connected with the adaptor 31 which is received in the chuck 42 of the drilling power tool 41 for transmitting a torque that is produced by a motor 43 of the drilling power tool 41 to the fastening element 11.

Finally, the fastening element 11 is rotated by the drilling power tool 41, via the adaptor 31, in a first rotational direction R1, whereby a borehole 7 in the constructional component 6 is formed (see FIG. 1).

After a desired borehole depth T has been reached, the transmission of the torque from the drilling power tool 41 to the fastening element 11 is interrupted. Through the feeding nose 46 of the ejection device, water under a high pressure is applied to the ejection piston 22 that is displaced in the direction of the first end 17 of the shaft 12. Thereby, the hardenable mass 15, which is located in the receiving space 14, is ejected from the fastening element 11 (see FIG. 2). The mass 15 exits through openings provided in the region of the first end 17 of the shaft 12 and/or in the drilling head 16 in the intermediate space 8 between the outer side of the shaft 12 and the wall of the borehole 7.

After the hardenable mass 15 has at least partially hardened, for tensioning of the fastening element 11, the adaptor 31 is again rotated by the drilling power tool 41, this time in a second rotational direction R2, by reversal of the rotational direction of the motor 43, with the rotational direction R2 being opposite to the rotational direction R1, and with the adaptor 31 being movable in direction of the first end 17 of the shaft 12. As soon as the adaptor 31 abuts the surface 9 of the constructional component 6, the further rotation of the adaptor 31 in the second rotational direction R2 provides for pre-stressing of the fastening element 11 to a desired amount (see FIG. 3).

A self-drilling, chemically anchorable fastening element 51 according to the present invention, which is shown in FIG. 4, has a shaft 52 with a receiving space 54 for a hardenable mass 55 storable in the fastening element 51, a drilling head 56 provided at a first end 57 of the shaft 52. Starting from the second end 58, the shaft 52 is provided with a first outer thread in form of a thread-shaped outer profile 59 extending over a portion of the shaft 52. Starting from the first end 57 of the shaft 52 and up to the first outer thread, there is provided on the shaft 52 a second outer thread also in form of a thread-shaped outer profile 60. The second outer thread extends in a direction opposite the direction the first outer thread extends. The pitch of the thread-shaped outer profile 59 that starts from the second end 58 of the shaft 52 is more flat than the pitch of the further thread-shaped outer profile 60.

Though the present invention was shown and described with references to the preferred embodiment, such is merely illustrative of the present invention and is not to be construed as a limitation thereof and various modifications of the present invention will be apparent to those skilled in the art. It is therefore not intended that the present invention be limited to the disclosed embodiment or details thereof, and the present invention includes all variations and/or alternative embodiments within the spirit and scope of the present invention as defined by the appended claims. 

1. A method of setting a self-drilling, chemically anchorable fastening element (11; 51) with use of a drilling power tool (41), the fastening element (11; 51) having a shaft (12; 52) with a receiving space (14; 54) for a hardenable mass (15; 55) provided in the fastening element (11; 51), a drilling head (16; 56) provided at a first end (17; 57) of the shaft (12; 52), and a thread-shaped outer profile (19; 59) provided at least partially at a second end (18, 58), the method comprising the steps: providing an adaptor (31) mountable on the second end (18; 58) of the shaft (12; 52) and having engagement means (32) for a chuck (42) of the drilling power tool (41) and provided on an outer side of the adaptor (31), and a thread-shaped inner profile (33) complementary to the thread-shaped outer profile (19; 59) on the shaft (12; 52); mounting of the adaptor (31) on the second end (18; 58) of the shaft (12; 52) of the fastening element (11; 51); connecting the drilling power tool (41) with the adaptor (31); drilling a borehole (7) in the constructional component (6) with the self-drilling fastening element (11; 51), rotating the fastening element (11; 51) in a first rotational direction (R1); forcing out the hardenable mass (15; 55) located in the receiving space (14; 54) from the fastening element (11; 51) with an ejection device; and pre-stressing the fastening element (11; 51) after at least partial hardening of the hardenable mass (15; 55) by rotating the adaptor (31) in a second rotational direction (R2) opposite the first rotational direction (R1), whereby at least a section of the adaptor (31) is displaced in a direction of the first end (17; 57) of the shaft (12; 52) of the fastening element.
 2. A setting method according to claim 1, wherein a stop (36) for the adaptor (31) is provided at the second end (18) of the shaft (12) of the fastening element (11).
 3. A setting method according to claim 1, wherein the drilling power tool (41) is provided with a constant motor (43) for drilling and pre-stressing.
 4. A setting method according to claim 1, wherein the thread-shaped outer profile (19; 59) at the second end of the shaft (12; 52) extends in a direction corresponding to the second rotational direction (R2).
 5. A self-drilling, chemically anchorable, fastening element, comprising a shaft (52) with a receiving space (14; 54) for a hardenable mass (15; 55) provided in the fastening element (11; 51); a drilling head (16; 56) provided at a first end (17; 57) of the shaft (12; 52); a thread-shaped outer profile (19; 59) provided at least partially at a second end (18, 58); and a further thread-shaped outer profile (60) extending from the first end (57) of the shaft (52) in a direction corresponding to a first rotational direction (R1) of the fastening element (52), the thread-shaped outer profile (59) that extends from the second end (58) of the shaft (52), extending in a direction opposite an extension direction of the further thread-shaped outer profile (60).
 6. A fastening element according to claim 5, wherein a pitch of the thread-shaped outer profile (59) extending from the second end (58) of the shaft (52) is flatter than a pitch of the further thread-shaped outer profile (60). 